Experimental study on parameterizing microplastic-sediment aggregation

The presence of microplastics in rivers and estuaries poses environmental challenges. To effectively address these challenges, it is important to identify microplastic sinks within the aquatic environment. This can be achieved through modeling the fate of microplastics with numerical transport models. A key process influencing their fate is microplastic-sediment aggregation. In this process, microplastics and sediments form flocs that are larger and denser compared to individual microplastics, leading to enhanced settling of microplastics in floc form.This research aims to parameterize microplastic sediment aggregation by conducting flocculation experiments in the lab. These experiments will involve microplastics in the form of fibers, fragments, and spheres with varying sizes and densities. Flocs will be generated by adding microplastics and sediment to a continuously stirred jar under organic-based, salt-induced, or combined flocculation conditions. Floc formation and growth will be continuously monitored using the Malvern Mastersizer to measure particle size distributions. The settling velocities of microplastic-sediment flocs will be determined using a settling column, coupled with a floc camera for detailed analysis.The results obtained from the experiments will be used to parameterize microplastic-sediment aggregation for different types of microplastics and conditions. This is achieved by using a novel method for parameterizing microplastic-sediment aggregation using the logistic growth model to describe floc formation and floc growth. By incorporating the parameterization of microplastic-sediment aggregation into numerical transport models, we aim to improve the accuracy of predicting the fate and transport of microplastics in aquatic environments.